1. Field of the Invention
The present invention relates to a screwstrip for use in an autofeed screwdriver.
2. Description of the Related Art
Screwstrips are known wherein the screws are connected together by a retaining belt preferably of plastic material and adapted to be fed into an autofeed screw fastening tool and successively driven from the belt as the screwstrip is advanced through the tool. Known screwstrips of this type include those referred to and disclosed in the present applicant's U.S. Pat. No. 5,758,768, issued Jun. 2, 1998 and U.S. Pat. No. 5,927,163, issued Jul. 27, 1999, the disclosures of which are incorporated herein by reference. Such screwstrips are adapted to be driven in autofeed screwdrivers, such as taught by the applicant's U.S. Pat. No. 5,568,753, issued Oct. 29, 1996, U.S. Pat. No. 5,934,162, issued Aug. 10, 1999 and U.S. Pat. No. 5,870,933, issued Feb. 16, 1999, the disclosures of which are incorporated herein by reference.
Such screwstrips in one form are disposed in a helical coil containing, for example, up to 500 screws to be placed in a canister to retain the screwstrip and from which canister, a lead end of the screwstrip is placed into the autofeed screwdriver and advanced thereto to drive successive screws.
Collated screwstrips are known in which the screws are connected to each other by a retaining strip of plastic material. Such strips are taught, for example, by U.S. Pat. No. 4,167,229, issued Sep. 11, 1979 and its related Canadian Patents 1,040,600 and 1,054,982, as well as U.S. Pat. No. 4,930,630, the disclosures of which are incorporated herein by reference. Screws carried in such screwstrips are adapted to be successively incrementally advanced to a position in alignment with, and to be engaged by, a bit of a reciprocating, rotating power screwdriver and screwed into a workpiece. In the course of the bit engaging the screws and driving it into a workpiece, the screw becomes detached from the plastic strip leaving the strip as a continuous length.
Conventional automated screwdrivers include a driver for advancing a screw strip. It is typical that the driver includes a finger, or pawl, which engages within slots formed in the edge of the screwstrip to advance the screwstrip. Once a driver has advanced the screwstrip to its forwardmost position for a given cycle, a screw in the screwstrip is aligned with the screwdriver head and is inserted by the screwdriver into the workpiece. Thereafter, the driver moves rearward to engage the next screwstrip and advance the screwstrip to position the next screw for insertion.
Conventional screwstrips include rectangular slots that are engaged by the feed pawl of the driver. Given the precise timing that is required, a feed pawl may hit the tailing edge of a slot as the driver is still retracting. This can pull the screwstrip rearward and result in a misfeed of the screwstrip. Alternatively, the feed pawl may miss slot entirely.